WebSVN – HelenOS – Path Comparison – / – /trunk/uspace/lib/libblock/ Rev 3594 and /trunk/uspace/lib/libblock/ Rev 3595

Ignore whitespace Rev 3594 → Rev 3595

 /trunk/uspace/lib/libblock/libblock.c
 ,10 → 296,13
  *
  * @param dev_handle        Device handle of the block device.
  * @param boff          Block offset.
+ * @param flags         If BLOCK_FLAGS_NOREAD is specified, block_get()
+ *              will not read the contents of the block from the
+ *              device.
  *
  * @return          Block structure.
  */
-block_t *block_get(dev_handle_t dev_handle, bn_t boff)
+block_t *block_get(dev_handle_t dev_handle, bn_t boff, int flags)
 {
     devcon_t *devcon;
     cache_t *cache;
 ,13 → 388,15
              */
             abort();    /* TODO: block_write() */
         }
-        /*
-         * The block contains old or no data. We need to read the new
-         * contents from the device.
-         */
-        rc = block_read(dev_handle, &bufpos, &buflen, &pos, b->data,
-            cache->block_size, cache->block_size);
-        assert(rc == EOK);
+        if (!(flags & BLOCK_FLAGS_NOREAD)) {
+            /*
+             * The block contains old or no data. We need to read
+             * the new contents from the device.
+             */
+            rc = block_read(dev_handle, &bufpos, &buflen, &pos,
+                b->data, cache->block_size, cache->block_size);
+            assert(rc == EOK);
+        }
         futex_up(&b->lock);
     }

 /trunk/uspace/lib/libblock/libblock.h
 ,6 → 44,22
 #include <libadt/hash_table.h>
 #include <libadt/list.h>
+/*
+ * Flags that can be used with block_get().
+ */
+/**
+ * This macro is a symbolic value for situations where no special flags are
+ * needed.
+ */
+#define BLOCK_FLAGS_NONE    0
+/**
+ * When the client of block_get() intends to overwrite the current contents of
+ * the block, this flag is used to avoid the unnecessary read.
+ */
+#define BLOCK_FLAGS_NOREAD  1
 typedef unsigned bn_t;  /**< Block number type. */
 typedef struct block {
 ,7 → 93,7
 extern int block_cache_init(dev_handle_t, size_t, unsigned);
-extern block_t *block_get(dev_handle_t, bn_t);
+extern block_t *block_get(dev_handle_t, bn_t, int flags);
 extern void block_put(block_t *);
 extern int block_read(int, off_t *, size_t *, off_t *, void *, size_t, size_t);